This invention relates to a process for the recovery of oil from subterranean oil bearing formations which may also contain highly saline and/or hard water, e.g. water containing appreciable quantities of sodium chloride and/or water soluble salts of divalent cations such as calcium or magnesium.
A large portion of the original oil in place in many oil-bearing subterranean formations remains in place after primary production and waterflooding. As oil reserves dwindle and exploration for new discoveries becomes more difficult and costly, the use of enhanced oil recovery techniques on previously discovered resources will play an increasingly important role in the overall production of crude oil.
Most of these techniques can be classified as solution flooding, mixture flooding, thermal oil recovery, tenside or polymer flooding or as a combination of several of these.
U.S. Pat. No. 3,335,792 discloses an oil recovery process wherein a foam bank is injected, followed by a non-gaseous dilute surfactant solution and then a further drive fluid.
U.S. Pat. No. 3,648,772 discloses a miscible-type recovery process using foam as a mobility buffer. The process uses a micellar dispersion followed by a foam and then a drive fluid.
U.S. Pat. No. 4,542,790 discloses a chemical flooding process using carboxymethylated ethoxylates as surfactants to control interfacial tension.